Arc arresting spark gap assembly for lightning arresters



Sept. 13, 1966 J. sAcER 3,273,010

ARC ARRESTING SPARK GAP ASSEMBLY FOR LIGHTNING ARRE$TERS Filed Nov. 22, 1965 INVENTOR JOZG SOJCQV' BY m ATTORNEYS United States Patent 3,273,010 ARC ARRESTING SPARK GAP ASSEMBLY FOR LIGHTNING ARRESTERS Joze Sacer, Neuenhof, Switzerland, assignor to Aktrengesellschaft Brown, Boveri & Cie., Baden, Switzerland, a joint-stock company Filed Nov. 22, 1963, Ser. No. 325,698 Claims priority, application Switzerland, Nov. 28, 1962, 13,950/ 62 6 Claims. (Cl. 315-36) The present invention relates to an improved arc arresting spark gap assembly for use in the construction of a lightning arrester.

For lightning arresters having multiple spark gaps and voltage-dependent resistances connected in circuit with each other, lower and lower response voltages and lower residual voltages are being required of late, in accordance with the regulations of various countries. With the assistance of the lower response voltages, the lightning arrester takes up the task of switching overloads, etc. However, because of the diminished ratio of the response voltage to the recovery network voltage, the requirements on the strength of the arc gap in resisting back-fire are in creased. The level of protection is reduced by the low residual voltage and thus the insulation of the apparatus becomes cheaper. The low residual voltage can be achieved on the one hand by an improvement in the materials from which the voltage-dependent resistances are formed, and on the other hand by a lessening in the amount of resistance utilized. But this must be obtained at the expense of an increase in the follow-current. The required increase in strength against re-ignition with stronger follow-currents places further requirements upon the arc gap which the regular plate type are gap structures used up to the present are no longer capable of handling. As a suitable expedient for increasing the arc quenching ability of the gap, more and more use is made of allowing the follow-current to wander off from its point of origin under the influence of a magnetic quenching field. The quenching field can be created either by suitable guidance of the follow-current in the electrodes, or by use of' special quenching coils fed by the follow-current, or by use of permanent type magnets. Of late, simultaneously with the wandering-0E of the are, a lengthening of the arc is also established. The thus forming high voltage across the arc reduces the follow-current and hence, relieves the resistors.

For an extension of the are, a stacked arc gap structure is known which comprises a plurality of plates of insulating material stacked in superposed relation, these insulating plates having an electrode on each side and so constructed that an electrode of one plate forms an arc gap with an electrode of the adjacent plate in the stack. The arcs formed in these gaps are under the influence of a common magnetic field generated by one or more quenching coils, and the arcs are moved toward the outer peripheries of the arc chambers formed by the stacked insulator plates, and are thus extended. For such an arrangement, electrodes of the divergent type are used, i.e. two electrodes forming one are gap are positioned at an angle to each other, e.g. at an angle of 90, so that they create a screw thread type of arc path around the longitudinal axis of the assembly of arc gaps.

The object of the present invention is to provide an improved arrangement for plate type lightning arrester arc gap structures which function without the necessity of providing a special quenching coil to establish the magnetic field, and which at the same time exhibit a considerably greater quenching ability than the known are gap stacks, this being accomplished by extending the arc to a degree heretofore not yet obtainable. Moreover, the resistance of the arrester to back-fire is also increased.

3,273,010 Patented Sept. 13, 1966 More particularly, the object of the invention is to provide an improved lightning arrester of the type utilizing voltage-dependent resistances and spark gaps wherein the arcs in the are gaps are extinguished by magnetic fields produced by the arcs themselves, there being a plurality of axially stacked plates of insulating material which have an electrode on each side and wherein quenching chambers are formed by the plates. In accordance with the invention, the aforementioned improvements are obtained by constructing the electrodes in an essentially hairpin i.e. U-shaped configuration, the legs of the electrodes having indentures to establish a response point for the arc, and the free ends of the legs being bent back upon themselves. These hairpin shaped electrodes are inserted into their respective insulating plates so that their two legs lie on opposite sides of the appertaining plate, and one leg of electrode together with the opposite leg of an adjacent electrode in the adjacent insulator plate always establish one are gap, all of the arc gaps thus formed being arranged axially one above the other.

The foregoing objects and advantages of the invention will become more apparent from the following description of a preferred embodiment thereof and from the accompanying drawings which illustrate the same. In these drawings:

FIG. 1 is a view in front elevation showing a stack of the insulator plates and their electrodes;

FIG. 2 is likewise a front view of one of the insulator plates showing the details of electrode insertion;

FIG. 3 is a top view of one of the insulator plates and its hairpin shaped electrode, the view being partly in plan and partly in section; and

FIG. 4 is a top plan view of one of the hairpin shaped electrodes.

With reference now to the drawings and to FIG. 1 in particular, the arc gaps are established with the help of a stack of insulator plates 1 having a cylindrical configuration arranged in superposed relation and co-axially. Each plate 1 is provided with a radially extending slot 2 into which a one-piece electrode pair 3 is inserted. Each electrode pair is seen from FIG. 4 to be constituted from a hairpin shaped electrode element, i.e. it is essentially U- shaped, and at like intermediate points along the two legs 3a indentures 4 are provided to form a point of response for the arc. The free ends of the legs 3a of each hairpin shaped electrode piece are bent back upon themselves to form horns 5. The electrode pairs 3 are inserted so that the legs 3a of the hairpin shaped electrode piece rest upon opposite faces of the corresponding insulator plate 1, the arrangement being such that one leg 3a of one electrode piece and its indentation 4 together with the opposite leg 3a and indentation 4 of the electrode piece inserted in the adjacent insulator plate 1 establish an arc gap. Between the legs and the bent-back parts 5 of the electrode pieces 3, separators 6 made of insulating material are provided, these separators being an integral part of insulator plate 1, and serving to prevent a short-circuit between the blasted arc and the electrode.

The insulator plates 1 are further designed so that insertion of the electrode pieces 3 is possible without bending them, and the necessary creep distance to adjacent electrodes is maintained by means of cavities. Moreover, the quenching chambers formed by the stack of insulator plates 1 are closed oil towards the exterior at the insertion slots 2 for the electrodes by means of projections at the circumference of the plates.

In a lightning arrester having the improved arc gap construction as explained above, magnetic quenching of the arcs is effected only through narrow loops of the arc in the plane of the quenching chamber individual to the response points 4 of each arc gap and by solenoid forma tion of adjacent arc gaps with good magnetic coupling. This magnetic field is fully sufiicient for moving the arc so as to extend its length so that a separate magnetic quenching facility is not necessary. The path of the arc after response of the arc gaps is indicated in FIG. 3 and is designated by the irregular line 7 from which it can be seen that the maximum length of arc in each arc gap surpasses the circumference of the corresponding quenching chamber and the arc voltage increases temporally until the arc is extinguished. This very advantageous effect results from the special shape and arrangement of the two-legged electrode elements 3 which are inserted into the insulator plates so that the legs of these elements are at least approximately parallel to a diametric axis of the plates 1 and extend from the insertion point 2 far into the opposite half of the insulating plate, after which the free ends are angled ofl? towards the outside so that always two arc loops, in the direction of the insertion point and at the circumference of the quenching chamber originate.

Another advantage of the improved construction in accordance with the invention resides in the fact that the two points of response 4 of each arc gap are separated by a great distance from the bending points of the electrode horns 5. This distance is greater than half of the length of leg 3a. Consequently, there is also a long distance between the points of response 4 and the are 7 and a small sight angle of the arc from the point of response through which are achieved a rapid electric stabilization of the point of response and an increased resistance to back-fire.

I claim:

1. In an arc arresting spark gap assembly for lightning arresters of the type wherein the spark gaps are connected in circuit with voltage-dependent resistances and quenching of the arcs in the gaps is eifected by an are produced magnetic field, the combination comprising a plurality of axially stacked cylindrical plates made from insulating material and an electrode piece inserted into each said plate, each said electrode piece being essentially of hairpin shape, the two legs of each electrode piece including an indenture forming a point of arc response and the free ends of the legs being bent back to establish horns, said two legs of each electrode piece being disposed substantially parallel to a diametral axis of the insulator plate and located respectively on opposite sides of the insulator plate in which it is inserted such that each arc gap is established by the indentures of respective legs of electrode pieces inserted in adjacent insulator plates, said legs of all of said electrode pieces having a length substantially exceeding the radius of said cylindrical insulator plates thereby to establish a maximum possible length of arc in each arc gap greater than the circumference of the quenching chamber formed within each adjacent pair of said insulator plates, and all of said are gaps being located axially one above the other.

2. An arc arresting spark gap assembly as defined in claim 1 wherein the distance between the response point of an arc gap and the bending point of the free ends of the corresponding hairpin shaped electrode piece is greater than half the length of one of the legs of said electrode piece.

3. An arc arresting spark gap assembly as defined in claim 1 wherein said insulator plates are provided with integral separator portions which lie between the legs and bent back end portions of said hairpin shaped electrode pieces.

4. An arc arresting spark gap assembly as defined in claim 1 wherein each said insulator plate is provided with a radially extending slot into which the corresponding hairpin shaped electrode piece is inserted.

5. An arc arresting spark gap assembly as defined in claim 4 wherein each said insulator plate is so configured as to enable the correspoding hairpin shaped electrode piece to be inserted in the slot thereof without bending.

6. An arc arresting spark gap assembly as defined in claim 1 wherein quenching chambers for the arc gaps are formed within said insulator plates which are generally cylindrical, and said quenching chambers are closed off toward the exterior at the insertion points of said electrode pieces by means of projections provided at the circumference of said plates.

References Cited by the Examiner UNITED STATES PATENTS 2,783,336 2/1957 Latour 3 l536 X 2,825,008 2/1958 Kalb 315-36 X 2,913,626 11/1959 Bislin 31536 2,917,662 12/1959 Cunningham 315-36 3,151,274 9/1964 Snell 31536 JOHN W. HUCKERT, Primary Examiner. I. D. KALLAM, A. J. JAMES, Assistant Examiners. 

1. IN AN ARC ARRESTING SPARK GAP ASSEMBLY FOR LIGHTNING ARRESTERS OF THE TYPE WHEREIN THE SPARK GAPS ARE CONNECTED IN CIRCUIT WITH VOLTAGE DEPENDENT RESISTANCES AND QUENCHING OF THE ARCS IN THE GAPS IS EFFECTED BY AN ARC PRODUCED MAGNETIC FIELD, THE COMBINATION COMPRISING A PLURALITY OF AXIALLY STACKED CYLINDRICAL PLATES MADE FROM INSULATING MATERIAL AND AN ELECTRODE PIECE INSERTED INTO EACH SAID PLATE EACH SAID ELECTRODE PIECE BEING ESSENTIALLY OF HAIRPIN SHAPE, THE TWO LEGS OF EACH ELECTRODE PIECE INCLUDING AN INDENTURE FORMING A POINT OF ARC RESPONSE AND THE FREE ENDS OF THE LEGS BEING BENT BACK TO ESTABLISH HORNS, SAID TWO LEGS OF EACH ELECTRODE PIECE BEING DISPOSED SUBSTANTIALLY PARALLEL TO A DIAMETRAL AXIS OF THE INSULATOR PLATE AND LOCATED RESPECTIVELY ON OPPOITE SIDES OF THE INSULATOR PLATE IN WHICH IT IS INSERTED SUCH THAT EACH ARC GAP IS ESTABLISHED BY THE INDENTURES OF RESPECTIVE LEGS OF ELECTRODE PIECES INSERTED IN ADJACENT INSULATOR PLATES, SAID LEGS OF ALL OF SAID ELECTRODE PIECES HAVING A LENGTH SUBSTANTIALLY EXCEEDING THE RADIUS OF SAID CYLINDRICAL INSULATOR PLATES THEREBY TO ESTABLISH A MAXIMUM POSSIBLE LENGTH OF ARC IN EACH ARC GAP GREATER THAN THE CIRCUMFERENCE OF THE QUENCHING CHAMBER FORMED WITHIN EACH ADJACENT PAIR OF SAID INSULATOR PLATES, AND ALL OF SAID ARC GAPS BEING LOCATED AXIALLY ONE ABOVE THE OTHER. 